Japanese Patent Laying-Open No. 2001-8380 (Patent Document 1) discloses a power management system where electric power can be transmitted between a battery of an electric vehicle and a house. In this power management system, a main controller on the house side determines the charging mode or the discharging mode, and a charging/discharging control signal is sent from a charging and discharging controller on the house side through a communication antenna to a battery controller on the vehicle side. The charging control or the discharging control is performed in the vehicle, based on the charging/discharging control signal received through the communication antenna (see Patent Document 1).
It is noted that the standard for the above-described electric vehicle that allows charging of the battery from the house is defined in “SAE Electric Vehicle Conductive Charge Coupler” (Non-Patent Document 1) in the United States of America, and in “Electric Vehicle Conductive Charging System, General Requirements” (Non-Patent Document 2) in Japan.
In these “SAE Electric Vehicle Conductive Charge Coupler” and “Electric Vehicle Conductive Charging System, General Requirements,” the standard for a control pilot is defined as an example. The control pilot is defined as a control line that connects, via a control circuit on the vehicle side, a ground of the vehicle and a control circuit of EVSE (Electric Vehicle Supply Equipment) for supplying electric power from an on-premises wiring to the vehicle. Based on a pilot signal communicated through this control line, a connection state of a charging cable, whether or not electric power is supplied from a power supply to the vehicle, a rated current of the EVSE and the like are determined.